Thank you for this help, much appreciated. I checked out Argus Monitor and it's webpage suggested it does everything needed, including controlling fans via the Asus extension board. I uninstalled AISuite 3 and Armoury Crate (a fairly laborious process to do...needed help via Google), then installed Argus Monitor. Unfortunately, there appear to be issues with this motherboard and Argus Monitor...
Under Argus Monitor's Settings/Mainboard/Fans Configuration, I see that if I select 'Nuvoton NCT6798' for the 'Source', only 7 controllable fans appear (others such as extension fans and water pump are missing). If I select 'Asus Service' for the 'source', I see the missing fans I want to control unfortunately, Argus Monitor does not allow me to control these fans, saying this source is read only.
--> 1. Can I ask Asus to tell me if they've locked out 3rd party fan controllers from working here? - this seems to be the case! (I'm also awaiting an email reply from Argus itself.
--> 2. I'm thinking this is an issue of other Asus motherboards too?